Benchmark LA4 line preamplifier

Upon hearing about this new product from Benchmark Media, the LA4, my mind turned to Laurindo Almeida, Bud Shank, Ray Brown, and Shelly Manne—the original L.A. Four jazz quartet. No such association was intended, however: the "4" merely designates change from previous Benchmark designs (footnote 1).

The LA4 is housed in a shoeboxy, half-rack chassis that stands apart from the contemporary hi-fi wide-and-flat norm. A large touchscreen, an engraved Benchmark logo, and a single large volume-control knob dominate the front. At the bottom left are a small on/off button and the IR sensor.

The action of the large knob is stepped, and an audible relay click accompanies each 0.5dB step change. I am accustomed, as perhaps many are, to smooth, silent operation, and I hastily concluded that the clicking would be intolerable. Nevertheless, I was wrong, especially as this construction contributes to some of the virtues I observed later.

All the other relevant external features are on the back: two pairs of balanced inputs (XLR), two pairs of unbalanced inputs (RCA), one pair each of balanced (XLR) and unbalanced (RCA) outputs, and a single mono balanced output that sums the stereo pair. There is also a pair of bidirectional 12V trigger jacks and an IEC power inlet.


But inside the LA4 lurks more interesting stuff, most notably that stepped volume control, which is based on arrays of precision resistors and sealed relays.

Control of Volume
The traditional audio volume control is a potentiometer in which a spring contact (wiper) is rotated along a curved, stationary resistive element, changing the amount of resistance in the signal path. For audiophiles, there are two concerns. The first is the reliability of the electrical connection between the wiper and the stationary element: Any compromise in contact integrity could result in distortion and/or nonlinear signal attenuation as the control is operated. The second concern, specific to stereo potentiometers, is how to maintain identical inputs/outputs for two potentiometers on a single shaft; often with potentiometer volume controls, the channel balance varies with the volume setting.

The most common way to deal with this in high-quality audio is to use a stepped attenuator that replaces the potentiometer with an array of discrete resistors and the spring- loaded wiper with a rotary switch. In volume controls like this, the signal still must pass through one or more switch contacts and, like the wiper, all need to maintain their integrity over a long duty cycle. Balanced circuitry has twice as many elements that need to be precisely paired and maintained. For multichannel control, the demands expand further.

The LA4's 16-step gain stage feeds a 256-step attenuator with 12 gold-contact relays and 64 precision (0.1%) thin-film resistors, switched by an array of 40 sealed, gold-contact precision relays. The use of physically large, metal-film resistors ensures rapid heat dissipation, preventing heat-induced increases in resistance values. The relays are controlled by an FPGA to ensure precise timing of relay switching, which Benchmark says reduces transient currents that can cause pops, clicks, and "zipper noise."

The LA4's design, the company says, ensures long-term, low-distortion, low-noise operation with accurate interchannel balance and repeatability. It also means that one can use multiple LA4s and know that they are accurately matched.

Using the LA4
Upon power-up, the LA4 displays the Benchmark splash screen that, after a few seconds, switches to the Main Screen dominated by the bold letters "LA4." The main screen shows the input selection by number and user-programmable name, the volume level by number and by a bargraph. The touch-sensitive screen has "buttons" for screen dimming, additional settings, balance setting, –20dB reduction, and muting. Tapping Settings takes you to three screens that access optional settings for Display, Input & Volume Setup, Power Control, Remote, and options for locking/resetting all.

The LA4's remote control is the same one supplied with the DAC3 in all its incarnations; it works with both the DAC and the LA4. When used with either the LA4 or the DAC3, the remote control's arrows allow the user to step through the inputs in either direction. Six discrete input buttons permit direct-access input selection, but these work only for the DAC3.

Footnote 1: The LA4 follows the HPA4 ($2999)—a very similar product, intended to drive headphones. The HPA4 followed on the heels of the Benchmark HPA1 and HPA2 headphone amps—but Benchmark skipped 3 to indicate a major change in chassis design and to avoid confusion with the company's DAC-3, one version of which, the HGC, incorporates the HPA2 headphone amplifier.
Benchmark Media Systems, Inc.
203 East Hampton Place, Ste. 2
Syracuse, NY 13206
(315) 437-6300

Bogolu Haranath's picture

Can it get any better than this for a pre-amp? ....... Add to the list, another nominee for Stereophile 2020 product of the year award, Benchmark LA4 ....... The headphone-amp output version Benchmark HPA4 was reviewed by Hi-Fi News :-) .........

supamark's picture

a riff on the classic Urei LA-4 compressor (both in name and form).

Kal Rubinson's picture

Seems to me coincidental. Line Amp 4 is a logical name and they do very different things. OTOH, the Urei is much better looking, imho.

Bogolu Haranath's picture

They could come up with a designer version and sell it for $20k :-) ........

dial's picture

Hello, yes I agree but the NAD recently reviewed is the ugliest for me.

Bogolu Haranath's picture

"Beauty is in the eye of the beholder" ......... Margaret Hungerford (1878) :-) ........

Poor Audiophile's picture

Please excuse an ignorant question, but these two are on the same CD? Or are they 2 different ones?

Kal Rubinson's picture

Same disc.

DH's picture

Very nice, You can stream it, too.

georgehifi's picture

"widest-dynamic-range I have encountered"

Hi JA, wouldn't it be more informative to know.
To compared it to the sources "direct connection measurement" dynamic ability. And then how much lower in dynamic range this preamp is going to measure.
As then these measurements would then mean something, that then tells you if your getting every morsel or close to it, of the sources dynamic swing that it has.

Cheers George

Bogolu Haranath's picture

According to JA1's measurements LA4 can pass through up to 20 to 21 bits of dynamic range signals, without any interference ....... In other words, LA4 doesn't 'editorialize' the passing signal :-) .......

Like KR said, it is 'super transparent' :-) .......

Douglas_Harrison's picture

I'd buy 1 in a heartbeat if they offered a 1 unit Multi-Channel option

Kal Rubinson's picture

Let's start a petition!

Bogolu Haranath's picture

May be you (KR) could also petition for a 8-channel Benchmark HGC DAC :-) .........

Kal Rubinson's picture

I have asked about 8channel DACs and preamps but I am only one voice.

Bogolu Haranath's picture

Who else could be more influential voice than KR for promoting multi-channel audio for music? :-) .......

Bogolu Haranath's picture

Andrew Quint from TAS could be the other influential reviewer/promoter for multi-channel audio for music :-) .......

Kal Rubinson's picture


Kal Rubinson's picture

Andy and I see eye-to-eye on many things.

Bogolu Haranath's picture

You both contribute to two very influential hi-end audio magazines .......Good idea to keep promoting surround sound for music ......... Let your voices be heard :-) .......

JRT's picture
Bogolu_Haranath wrote:

"...petition for a 8-channel Benchmark HGC DAC"

This one looks interesting, if you have a relatively simple system that only needs eight channels of PCM.

Bogolu Haranath's picture

Yes ...... DAC8 Pro also does DSD 128 in addition to PCM ........ Audio Science Review gave the Okto Research DAC8 Pro a glowing review ........ May be KR could also review it :-) ......

Kal Rubinson's picture

The production Okto DAC8 Pro is on the way to me. FWIW, ASR reviewed a prototype, I believe, since it was done months before any product was shipped to customers.

Bogolu Haranath's picture

Looking forward to reading your review ...... Question is, would JA1 measure it? :-) ........

JRT's picture

Kal, I am looking forward to your review and JA1's measurements of the Okto Research DAC8 Pro. And I am hoping that they find a better means of selling into the US market, as I would prefer to buy from a domestic source rather than play with overseas mailorder.

Kal Rubinson's picture

Yeah. Unfortunately, it is not likely that a product with no US dealers and available only from overseas web/mailorder will qualify for a full review.

JRT's picture

You know your business and are probably right in your statement.

Perhaps, on electronics assemblies (not loudspeakers), Stereophile might consider further relaxing those requirements to better accommodate the global economy and modern changes in business models.

Kal Rubinson's picture

It is not my decision to make but I do know that the editors are aware of the issues and are considering options.

georgehifi's picture

Any "active circuitry in an analog preamp" has to impact the dynamic range a little compared to the source going direct to the amps, unless there is some kind of "dynamic range expansion" circuitry inside to make up for any losses, and I doubt that very much, as they sound ****.

Cheers George

Kal Rubinson's picture

In a perfect world, there would be no need for Any "active circuitry in an analog preamp".

Bogolu Haranath's picture

It would be interesting to see a follow-up review by KR with dCS Bartok or Rossini players with LA4 ...... Both those dCS players have digital volume controls ....... KR could compare their sound with and without LA4 in the signal path :-) .......

Bogolu Haranath's picture

Both of those dCS players have approximately the same SNR as LA4 :-) ........

Kal Rubinson's picture

I suspect that the exaSound is in the same class. See:

Bogolu Haranath's picture

I could not find any Stereophile measurements of exaSound ....... I saw your (KR) reviews of exaSound for Stereophile :-) ........

Bogolu Haranath's picture

Instead of dCS, you (KR) could compare LA4 with the Benchmark DAC3 HGC, DAC/headphone-amp/pre-amp ...... After measuring the DAC3 HGC, JA1 said, "Wow" ...... Need I say more? :-) .......

Kal Rubinson's picture

Not likely as I do not have any of those "in house."

There have been measurements of the e32 at Audio Science Review Forum, fwiw.

Herb Reichert's picture

there would be no need for extra amplifier gain stages - just to make gain for feedback

or 49 output devices - just to drive inefficient speakers with complex crossovers



Kal Rubinson's picture

True dat but these are the consequences of history as well as of other choices we make. Change can come from a complete re-imagining of system topology. Until then, each component has to be respectful of what comes before it and what follows.

Bogolu Haranath's picture

Like 'cruise control'? ....... See Benchmark media blog about 'feed forward' technology used in their amplifiers :-) ....... ........

Bogolu Haranath's picture

If you want to see how feedback levels change the FR and distortion levels, see JA1's measurements of CH Precision integrated amp measurements :-) ........

Bogolu Haranath's picture

The manufacturer (Benchmark) talks about using 'active buffering', actually to reduce the noise levels ...... See, manufacturer's comments in the print edition of January 2020 Stereophile ........ JA1's measurements show 20 to 21 bits of SNR (dynamic range) ........ It would be nice to see manufacturer's comments included in the web postings of the reviews, BTW :-) .......

Jim Austin's picture

from an Application Note. I doubt they'll mind my quoting it here at significant length:

Most people understand that active buffers create some noise and distortion. But many people falsely assume that these active components are the only source of noise and distortion in an audio circuit. The truth is that passive components are usually the primary source of noise and distortion in an audio circuit!

In a search for perfection, many audiophiles have bought into the "fully passive" myth. I suspect that this explains why most relay attenuators are fully passive. On the surface, "fully passive" sounds like a good idea.

What many audiophiles don't realize is that a single resistor can create far more noise than a good active buffer. For example, an LME49860 opamp produces about the same noise as a 440-Ohm resistor. This means that the LME49860 is 13.6 dB quieter than the thermal noise produced by a single 10 k resistor! Buffers can allow the use of much lower impedances in an attenuator's resistor ladder network. When the impedances are reduced, an active design can be far quieter than a fully-passive design. Low-noise can only be achieved when resistors have very low impedances and signal levels are kept high.

If the impedances are reduced in an fully-passive attenuator design, the noise can be reduced but distortion will increase. This distortion is caused by an overloading of the upstream device. When an audio output is overloaded, distortion increases. Contrary to popular myth, distortion can be reduced by adding high-quality active buffers.

A third problem with passive attenuators is that they may not provide enough drive for downstream devices. Cable capacitance and input capacitance can cause a high-frequency roll off. Worse yet, the frequency response may change as the volume is adjusted with a passive attenuator. Low output impedance is important for maintaining a wide bandwidth. Output buffers are essential for delivering a predictable frequency response.

Jim Austin, Editor

Bogolu Haranath's picture

It is interesting to read, JA1's review and measurements of Ayre Acoustics KXR-Twenty pre-amp ...... Charles Hansen's (manufacturer) approach and his discussion about pre-amp design are an interesting read ...... Also, Ayre previous design KXR pre-amp review and measurements are an interesting read, as well :-) ......

Long-time listener's picture

Mr. Rubinson, I notice that in the past you have used much more expensive Audioquest speaker cables, perhaps in a different system. Could you please give your impressions of the Blue Jeans speaker cables? Thank you

Kal Rubinson's picture

I ordered them with only one end terminated because I wanted an unusual termination on the other end. They supplement/complement a pair of Benchmark NL2 TO BANANA - 2 POLE cables which can be used only with the Benchmark amp. Both sets use the same bananas and the same cable (Canare 4S11) and, not surprisingly, they sound identical.

I stopped using the AQs only because their stiffness and their bulky connectors make them inconvenient with my new Revel Studio2 speakers which have a cover/door over the speaker terminals that I'd like to close for cosmetic reasons.

I will say that I do not hear any change but I am a cable (difference) denier. At audio frequencies, any competent cable should sound the same, imho. You might consider it a bias. I do not.

Long-time listener's picture

Thanks for taking the time to respond--I should have remembered that you are a "denier." As far as cables go, I think your term "competent" potentially covers a lot of territory, and perhaps "competent" cables "should" sound about the same--just as all "competent" preamps should aim for the same transparency as this Benchmark preamp. Life would certainly be easier for me if I could be a denier too, but I can't. Over a long period of time, and with different equipment, I have found that my $1,200 Siltech interconnects consistently sound marginally more transparent, but also less warm and full-bodied, than my $600 Ortofon ones. I wish the Siltechs sounded better to me: they look nicer and cost more, but I generally use the Ortofons.

Yes, I do consider your outlook a bias. Remember, serious reviewers of stereo equipment once said the same thing about amplifiers that you say about cables, which is that any two competently designed amplifiers "should" sound the same. Perhaps they "should," but they don't. Today we certainly consider that viewpoint a serious bias. Best regards, LTL

Long-time listener's picture

...It seems to me that as soon as you say some cables are "competent," and others aren't, that you've already admitted there are differences between cables. And further, you seem to be saying that all the competent ones are not only competent, but perfect too--they're all so good that they sound absolutely identical. Does that really make sense? Your own comments seem to contradict your idea that there is no difference.

Kal Rubinson's picture

I would define "competence," in this case by mechanical and electrical engineering standards, and, yes, the competent ones are probably closer to perfection than is required by the rest of the audio chain. This, of course, is not the best forum for such a discussion but my position is based on my experience, just as is yours.

Ortofan's picture

... one need?
What is the difference between the noise floor of your listening room and the peak output capability of your power amp and speakers?

Would the performance of a sub-$400 pre-amp, such as the Pro-Ject Pre Box S2 Analog(ue) or the Parasound Zpre3 be sufficient - and indistinguishable from the Benchmark unit?

Bogolu Haranath's picture

32 bits, which is SNR of 192 :-) .......

jeffhenning's picture

To answer your question straight off, no.

Would it be good enough for you? Very possibly.

If you listen to music regularly at 110dB, your hearing will suffer in a few years or less.

A 100dB is actually pretty loud, but not deafening. It still may cause hearing damage, but will take much longer.

Most speakers (not horn-loaded), start to achieve their maximum output level around 104-110dB. This is a broad generalization, but, for the most part true.

If you are listening to music and the octaves around 1kHz are hovering at 100dB, then there is a really good chance that the bass one decade lower (100Hz) is about 10-12dB higher.

After looking at this for a decade (time, not frequency), I've come to the conclusion that music, live or recorded, sounds best when it has equal energy per octave... like pink noise. This again is a generalization, but it seems to work almost all the time for me.

In a really great listening room or recording studio, the background noise is going to be between 10 to 20dB. That does seem like a lot, given that the standard threshold for audibility in humans is 0dB, but trying to achieve that in the real world is very difficult. Cars, busses, over-flying planes & helicopters, dogs, cats, squirrels and people walking by with those animals make noise. And that's just outside your place.

Inside, you have a refrigerator, water heater and house heaters to deal with. Not to mention air conditioning when it's really hot and, when not, you'll have windows open somewhere.

My main audio system is in my basement. Generally, the quiescent noise in it is around 25-30dB when nothing is running.

Unless you are going to create a purpose-built room with no windows, incredibly expensive air-driven HVAC and have it inside something akin to a concrete bunker inside a larger concrete bunker, you won't get significantly better than my basement when nothing is running.

So, looking at all of this, why do you need a pre-amp better than the Project Audio or Parasound?

Perhaps, you personally, do not. This is not a cut on you, but not everyone has the same hearing acuity and, if you are living in the city, the background drone is going to be pretty high regardless of how many floors your apartment is from the street.

When it comes just to noise, that is usually (and should be) a steady state for any component. I'm pretty sure this Benchmark unit crushes the units you mentioned. It should given its price.

What you should really be looking at, though, is its distortion measurements. Those will give you the idea about how this unit sounds. I think that JA already stated that better than me.

Distortion is not steady state. It's dynamic and, unlike noise (which you can accommodate and then ignore somewhat in your brain), distortion of all types is undesirable in a h-fi component. It is coloration. While it can be benign, sometimes it's not.

Given what I know about the two pre-amps you mentioned, I'm sure that, until you build your bunker in a bunker, they would be fine.

With 110dB being the loudest you will play your system, the dynamic range of the average dwelling might only be, optimally, 85dB.

This, then, is where it gets very hairy. The noise in your place is not a stream of pink noise. It is also dynamic and generally centered around various, random frequencies below 1kHz. So the mids and highs have less noise intruding upon them.

Humans also can distinguish sounds way below the current noise of standard life. Sometimes up to 30dB into and below the background noise.

So, a pre-amp with 120dB dynamic range is actually what you need if you have the listening room to allow it to give you the best performance.

That does not mean that you can't enjoy music in noisier environments with equipment that has more noise. I did that for a few decades.

This is a great time to be an audiophile if you buy stuff like that made by Benchmark.

As Don Fagen sang, "What a beautiful world it will be, what glorious time to be free."

Ortofan's picture

... Benchmark quotes the S/N as 116dB (A weighted) when using the unbalanced outputs (vs. 137dB when using the balanced outputs) and a THD spec of 0.00005% (when using the balanced outputs - no THD spec is stated when using the unbalanced outputs) for an output level of 2V rms at 1kHz.

Pro-Ject specifies a "noise floor" of 105dB (A weighted) and THD of 0.0005%. Test conditions are not explicitly stated, but mention is made of "output voltage typically: 1V at 1kHz". The Pro-Ject unit only handles unbalanced signals. Their product literature claims "neutral sound with superior low noise floor" and "incredibly low harmonic distortion levels guarantee a listening experience which has never been available in this price range."

Bogolu Haranath's picture

Pro-Ject Pre-Box S2 doesn't have any analog inputs and so, cannot be used as an analog pre-amp ...... not exactly apples to apples comparison :-) ........

Ortofan's picture

... three analog inputs.

Are you, perhaps, mistakenly looking at the Pre-Box S2 Digital?

Bogolu Haranath's picture

Oops .... I didn't see your earlier comment ..... I assumed it was Pre-Box S2 Digital, which was reviewed and measured by Stereophile ...... I could not find any measurements of S2 analog ...... Given the very good measurements of S2 Digital by Stereophile, most likely the analog S2 could have very good measurements also ...... There is a DS2 version of Pre-Box analog, which has more inputs for, $550 ......... Anyway, none of the Pre-Box analog versions have balanced inputs and outputs like the Benchmark LA4 :-) ........

Ortofan's picture

... you replied to it.

For about $2,000 above the price of the Pro-Ject Pre Box S2 Analogue, you can buy the Benchmark unit and get balanced inputs and outputs, which will have better noise performance.

But the question remains, does the rest of your system allow you really take advantage of the extra dynamic range from the lower noise floor with those balanced connections?

Bogolu Haranath's picture

Yes, I saw your earlier comment, but I missed the 'analog' part of it ....... Ok, from now on I will read your comments word by word, may be even half a dozen times, before I make my comments/replies ....... I didn't say it makes any significant 'audible' difference at such very low noise levels ...... Balanced connections not only reduce common mode noise levels, but also make more secure connections ........ As far as the price is concerned, it is up to the buyers to make that decision ....... I would say Benchmark makes reasonably priced gear for all that performance their gear offers :-) .......

Bogolu Haranath's picture

I forgot to mention ........ Benchmark LA4 also offers 256-step technically advanced volume control :-) .......

Bogolu Haranath's picture

A better comparison for Pro-Ject Pre-Box S2 would be the Benchmark DAC3 HGC ...... Even so, DAC3 HGC has two analog inputs and can also be used as an analog pre-amp :-) .......

Bogolu Haranath's picture

A better comparison for Pro-Ject Pre-Box S2 would be the new iFi Audio Zen DAC/headphone-amp/pre-amp, $130 :-) .......

Glotz's picture

So funny...

Thanks man!

The Benchmark website has all of the manuals for the current lineup, and full measurements and descriptions / interpretations. These are an excellent compliment to JA's Measurements section.

In fact, the whole website is an eye-opener, especially their cable area! I am intrigued.

FredisDead's picture

The debate is like dirt in a horse corral; a mixture of ancient alluvial soil and recent organic waste. JA measures and the rest of us spend our money. JA measures what he can measure. The rest of us listen. The people who have bought Benchmark products based upon their belief structure in measurements have largely been bored by the result. Noise is not evil. Noise is ever-present and a good thing. It is the glue that holds music together. The place for headroom happens to lie with transducers and recordings, not electronics. I admire JA. I truly do. But he is a man trapped within his own skill-set. That has always been his primary limitation as an equipment reviewer. That limitation has been far eclipsed by his editorial skills. I urge all of you hell-bent on buying this preamp based upon JA's measurements to borrow one first and listen for a month. If you don't, there is a very good chance it will end up for sale on the used secondary market.

Kal Rubinson's picture


Dunno where the data for that statement comes from but it seems to imply that there is an inverse relationship between good measurements and satisfying sound and that is unreasonable.


Always good advice for any significant purchase. I will note that I reviewed it before JA measured it and would certainly buy one if I did not need 4 of them!

FredisDead's picture

ever-present on the used market for years. Then the fervor died down. JA's measurements of amps and preamps are rather innocuous; they tend to more or less correlate (i.e. not compete) with SQ upon lengthy subjective listening. JA's measurements of DAC's and loud speakers have always conflicted with long term listening impressions. So here we are with a line stage. It is probably fine but still, at the end of the day, boring and sterile. Sort of like a typical septuagenerian in need of vigorous exercise, a better diet, and some viagra.

Jason Victor Serinus's picture

Glad to know that I'm atypical...

Kal Rubinson's picture

Was that ever in doubt? :-)

Bogolu Haranath's picture

Thou shall not 'covet' expensive audio equipment :-) .........

Ortofan's picture

... hold your music together?

Is there some optimal level of noise below which, to your ear, the notes fall apart and above which the musical message is obscured or impaired?

Don't certain equipment reviews extol the virtues of those products that exhibit a "blacker background" - or, in other words, generate less intrinsic noise and distortion?

Bogolu Haranath's picture

Those same reviewers 'extol' the virtues of 'blacker backgrounds' whenever they review any new interconnect, any new speaker cable, any new isolation device, any new equipment rack, any new power purifier, any new ........ and, the list goes on :-) ........

Glotz's picture

As a headphone amp borrowing tech from the AHB2 power amp, the unit is incredibly resolving. THX developed a different approach for all of their new amplification line. The collateral information on their website is comprehensive and convincing from many perspectives.

It would seem that the implementation of feedback here has been handled very differently as the measurements suggest. Noise of a superfluous nature is bad, if it's not needed in a design to achieve the design goals.

Other amps sound fantastic with other approaches towards the use of feedback. They usually measure well, too.

After a week of ownership of the HPA4 (THX-88 headphone amp + LA4), I concur that this preamp is quite transparent to sources. If I add a tubed phone preamp or perhaps the PS Audio Stellar as a source, I can more effectively tailor the sound to my preference, combining a transparent line and hp stage with a luscious or straight phonostage, dac or whatever.

I am looking at the AHB2 for amps in the next few months, but what stops me from auditioning (or purchasing to audition) a Rogue Audio Stereo 100 tubed power amp and see how that integrates with my system, both in front of my MG 1.6's or in back of the HPA4? It's the same risk invested to auditioning at a dealer and then purchasing and re-auditioning in one's home.

JA1 was never relegated to anything. It's up to us to determine where a given measurement and a given component applies to one's preference in shaping a stereo system.